The objectives of these studies are primarily three-fold: (1) to define the role of B and T cells in immune mechanisms to a syngeneic line of malignant lymphocytes (Ib cells) in C58 mice; (2) to determine the immunosuppressive effect of chemotherapeutic drugs on B and T cell functions in immunity to leukemia; and (3) to determine if poly A:U can restore drug-suppressed immunocompetence.